Longbow skills 3 and 4 can be fired behind the guardian while running forward.
I imagine this is unintended as other weapons cannot fire projectiles backwards.
Note: these are ground targeted skills and not player targets, which may be why it is happening.
This is similar to how the warrior used to be able to throw the greatsword 4 at targets behind the character. The gs throw was patched to just be a cd.
K Pop
The Warrior, The Necro, The F1 Connoisseur
http://www.twitch.tv/interpretinterrupt